Foundation for a brick shed

[Shinogi]

OK, lovely. So much bad reading about clay that foundations have to be quite deep but I guess my build isn't a house so it's not as bad.

I'm starting to order the stuff now. Two sides of the foundation though will be against a brick wall which is my neighbours wall. Their garden is lower than mine so the brick wall will be deeper than my foundations will be. Am I alright putting my foundations against the wall or will i have to come away from it about 300mm or something?

 

[pinenot]

Step the two strips down to the wall strips, and build up with brick/blocks to suit, much more stable...pinenot

 

[banjodeano]

Work out the depth required to build the substructure up to dpc level, and dig to that depth into the clay (remember you'll have mortar joint forbye the bricks/blocks height to add on)...pinenot

To banjodeo - there are no shutters so to speak forming side walls for strip founds, you simply use the trench walls i.e. a 600 strip is nominal

Sorry for jumping in on your post Shinogi..
Pinenot, thanks for that info, yes your right, but i was thinking about my own project and sort of got mixed up, i want to lay one large slab of concrete, so i was thinking i could do it in two parts, and wondered if i had to join the two parts with mesh, and wondered how i could do it, and if in fact it would need joining at all....
sorry once again Shinogi.

 

[Shinogi]

Step the two strips down to the wall strips, and build up with brick/blocks to suit, much more stable...pinenot

Not quite sure what you mean. Are you saying to dig down to the side of the walls foundations and put mine alongside or something different. You're the professional and I'm the novice so I can't quite grasp what you mean by that, I feel silly now

 

[theoldun]

Hi, I'm just starting a brick shed build and I need a little advice for the foundations.
]

Word of warning fellow. If you are building single storey building with brick, block cavity wall, then suggest you take a lot of the advice given here with a pinch of salt.
Building Regss are rather vague in the requirements of foundation depths, but we list below an extract from Approved Document part A. section 2E4

In clay soils subject to volume change on drying (‘shrinkable clays’, with Plasticity Index greater than or equal to 10%), strip foundations should be taken to a depth where anticipated ground movements will not impair the stability of any part of the building taking due consideration of the influence of vegetation and trees on the ground.
The depth to the underside of foundations on clay soils should not be less than 0.75m, although this depth will commonly need to be increased in order to transfer the loading onto
satisfactory ground.

NHBC are more descriptive with regard foundation depth in clay soils and we list below their recommendations and requirements.

High volume change potential 1.0 metre deep..
Medium change potential 900nn deep.
Low change potential 750mm deep.

As we have no idea of the plasticity index in your area suggest you take the medium change potential and make your dig 900mm below existing ground level. Your choice.

You do not need rebar or fabric mesh. Always try to avoid day joints
Regards oldun

 

[Shinogi]

So you're saying that if I take my foundations depth to 1 meter, I should be good to go? There is so much contradicting information on clay soils on the internet. Some say it's the best ground to build on, some say it's the worst. My neighbour has a normal single block shed built on very shallow foundations but I guess mine would have more weight.

I know you say to avoid a day joint and I thought it's best to have the foundations laid all in one go but I don't think it's feasible for my access to the site so a day joint may have to be used. I don't mind digging the extra depth, it's getting the amount of cement I need in there.

Thank you for the information regarding depths, it's appreciated and put things into a little more perspective. It did sound all too easy.

 

[pinenot]

If your project requires it you could combine the two part pour with an incorporated expansion joint, otherwise you simply have to do the staggered joint - View media item 60174 ...pinenot

 

[pinenot]

Your building a shed, I've built 4 storey buildings on clay.
And as far as I know NHBC are still an insurance cocern/company for house building waiting in the wings to take over from BC. Bye the way my found digs were inspected by BC prior to any pour, clay as described by you was acceptable in all cases...the choice is yours I'm suggesting you take your dig down to the level of your neighbours wall founds, which you've intimated has been up for some time? do the maths...pinenot

 

[Shinogi]

The neighbors garden is about 700mm lower than mine so from my side, the foundations for it will be very deep but from her side, I presume it's not very deep at all. Having a chat with my other neighbour and he said he didn't dig very deep at all but can't remember the depth he went to.

I think I'll stick with your advice pinenot, it does make sense. Even though it would be nice to just dig a deep trench, the over all extra work doesn't make much sense with how everything else sits on this clay.

 

[Shinogi]

Am I right in thinking I wouldn't need planning permission or building regs for what I intend to build? I've checked the planning portal and i'm pretty confident I can with the rules for upto a 30m2 shed.

I'm poised ready to dig, I'm thinking of going to the council to confirm but I'm sure, going by the planing portal, I'm free to build with minimal restrictions i.e 2.5m high.

 

[Shinogi]

pinenot, you are right my friend

I have dug down next to the old wall that I will be building next to and the bottom of the foundation is only 370mm deep and only consists of bricks laid on their sides (100mm) on which the wall is sat on. There is only a 15mm gap either side between the edge of the bricks (foundation) to the actual wall bricks so the ground should be solid enough for me to build on with no worries at all with wider foundations. Just to note, this wall is 1500mm high. (The wall needs repointing first though before i build next to it.)

The top of the foundation (bricks) is level with the start of the clay so they dug into it a little which is what i need to do anyway thanks to pinenots' advice. I'll probably be digging slightly past that anyway for my foundations.

Thank you for all your advice pinenot

 

[pinenot]

Your very welcome shinogi

 

[Shinogi]

How do I work out my total floor space? I've got a cavity wall, is it from the inside of the outside brick or the inside of the inside block? Can't go above 30m2 so I need to know for sure

 

[pinenot]

Floor space - as the wording suggests is the available usable floor i.e. inside the walls - but this is presumably in response to a planning rule of the local authority?? best check the wording of rule, just to be on the safe side...pinenot

 

[Shinogi]

Yes, it is a rule for my build. To build the brick shed without building regulations approval, the "floor area" has to be no larger than 30m2.

Quote from planning portal

"If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building contains NO sleeping accommodation and is either at least one metre from any boundary or it is constructed of substantially non-combustible materials."

I've been to my local cuncil to ask if my build is ok to go ahead with no ermission etc.. and they I had to make an appointment for them to ring me back. That was 2 weeks ago and no call so I can't ask them to be sure.

I'll look into it a bit moe, thanks pinenot